diff --git a/src/main.cpp b/src/main.cpp
index 2b2c113..e1d3c7a 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -42,6 +42,10 @@ uint8_t temprature_sens_read();
 
 static const char* TAG = "MAIN";
 
+
+#define TIME_TO_SLEEP  60  // seconds
+constexpr unsigned int dhcp_interval = 60*60;
+
 WiFiMulti wifiMulti;
 GxEPD2_BW<GxEPD2_213_B72, GxEPD2_213_B72::HEIGHT> display(GxEPD2_213_B72(/*CS=SS*/ TFT_CS, /*DC=*/ TFT_DC, /*RST=*/ TFT_RST, /*BUSY=*/ -1)); // GDEH0213B72
 static constexpr uint8_t y_offset = 6;
@@ -56,6 +60,18 @@ BH1750 lightMeter;
 XD0OTA ota("esp32-weatherstation");
 XD0MQTT mqtt;
 
+struct __attribute__((packed)) network_t {
+  uint32_t ip;
+  uint32_t dns;
+  uint32_t gateway;
+  uint32_t subnet;
+  char ssid[64];
+  char password[64];
+  int32_t channel;
+  time_t last_dhcp;
+};
+RTC_DATA_ATTR network_t network;
+
 struct __attribute__((packed)) sensor_readings_t {
   float temperature = NAN; // °C
   float humidity = NAN; // %H
@@ -79,15 +95,111 @@ sensor_readings_t sensors_a4cf1211c3e4, sensors_246f28d1fa5c, sensors_246f28d1a0
 
 SensorHistory history_pressure(30);
 
-uint32_t lastDisplayUpdate = 0;
-uint32_t lastDisplayRefresh = 0;
-bool bme280_active = false;
-bool bme680_active = false;
-bool uv_active = false;
-bool light_active = false;
-bool sds_active = false;
+RTC_DATA_ATTR time_t lastDisplayRefresh = 0;
+struct __attribute__((packed)) sensors_active_t {
+  bool bme280 = false;
+  bool bme680 = false;
+  bool uv = false;
+  bool light = false;
+  bool sds = false;
+};
+RTC_DATA_ATTR sensors_active_t sensors_active;
 
 float station_height = 0;
+RTC_DATA_ATTR int bootCount = 0;
+
+
+time_t getTimestamp() {
+  struct timeval tv;
+  gettimeofday(&tv, NULL);
+  return tv.tv_sec;
+}
+
+
+void poweroffDevices() {
+  display.powerOff();
+
+  // ToDo: Sensors
+}
+
+
+void gotoSleep(unsigned int sleep_time = TIME_TO_SLEEP) {
+  mqtt.end();
+  WiFi.disconnect();
+  WiFi.mode(WIFI_OFF);
+
+  poweroffDevices();
+
+  //rtc_gpio_isolate(GPIO_NUM_12);
+
+  esp_sleep_enable_timer_wakeup(sleep_time * 1000000LL);
+  esp_sleep_pd_config(ESP_PD_DOMAIN_RTC_PERIPH, ESP_PD_OPTION_OFF);
+  Serial.println("going to to sleep for " + String(sleep_time) +
+  " Seconds");
+  Serial.flush();
+  esp_deep_sleep_start();
+  delay(1);
+}
+
+void wifiConnect() {
+  WiFi.persistent(false);
+  WiFi.setHostname("esp32-weatherstation");
+
+  wifiMulti.addAP(WIFI_SSID, WIFI_PASSWD);
+  wifiMulti.addAP(WIFI_SSID2, WIFI_PASSWD2);
+  wifiMulti.addAP(WIFI_SSID3, WIFI_PASSWD3);
+
+  IPAddress ip = IPAddress(network.ip);
+  IPAddress dns = IPAddress(network.dns);
+  IPAddress subnet = IPAddress(network.subnet);
+  IPAddress gateway = IPAddress(network.gateway);
+
+  Serial.println("millis(): " + String(millis()));
+
+  Serial.println("previous dhcp: " + String(getTimestamp() - network.last_dhcp) + "s ago");
+
+  if ( ip != INADDR_NONE && dns != INADDR_NONE && gateway != INADDR_NONE && subnet != INADDR_NONE
+       && ((ip[0] == 192 && ip[1] == 168) || (ip[0] == 172 && ip[1] == 16))
+       && strlen(network.ssid) > 0 && strlen(network.password) > 0
+       && (getTimestamp() - network.last_dhcp < dhcp_interval)
+     ) {
+
+    ESP_LOGD("WiFi", "STATIC IP");
+    WiFi.config(ip, gateway, subnet, dns);
+    WiFi.begin(network.ssid, network.password, network.channel);
+    for (int tries=0; WiFi.status() != WL_CONNECTED && tries < 10; tries++) {
+      ESP_LOGD("WiFi", ".");
+      delay(500);
+    }
+  } else {
+    ESP_LOGD("WiFi", "DHCP");
+    for (int tries=0; wifiMulti.run() != WL_CONNECTED && tries < 20; tries++) {
+      Serial.print(".");
+      delay(500);
+    }
+
+    network.ip = (uint32_t)WiFi.localIP();
+    network.dns = (uint32_t)WiFi.dnsIP();
+    network.gateway = (uint32_t)WiFi.gatewayIP();
+    network.subnet = (uint32_t)WiFi.subnetMask();
+    strncpy(network.ssid, WiFi.SSID().c_str(), 64);
+    strncpy(network.password, WiFi.psk().c_str(), 64);
+    network.channel = WiFi.channel();
+    network.last_dhcp = getTimestamp();
+  }
+
+  Serial.println("millis(): " + String(millis()));
+
+  if(WiFi.status() == WL_CONNECTED) {
+    ESP_LOGD("WiFi", "connected");
+    //ESP_LOGD("WiFi", (WiFi.localIP().toString().c_str()));
+
+  } else {
+    ESP_LOGE("WiFi", "could not connect to WiFi");
+    ESP_LOGE(TAG, "restarting");
+    ESP.restart();
+  }
+}
 
 void helloWorld()
 {
@@ -101,7 +213,11 @@ void helloWorld()
   // center bounding box by transposition of origin:
   uint16_t x = ((display.width() - tbw) / 2) - tbx;
   uint16_t y = ((display.height() - tbh) / 2) - tby;
-  display.setFullWindow();
+  if (display.epd2.hasFastPartialUpdate) {
+    display.setPartialWindow(0, 0, display.width(), display.height());
+  } else {
+    display.setFullWindow();
+  }
   display.firstPage();
   do
   {
@@ -139,13 +255,14 @@ void getTime(char* ptr, size_t maxsize, const char* format) {
 
 
 void getSensorMeasurements() {
-  if (bme280_active) {
+  if (sensors_active.bme280) {
     bme280.takeForcedMeasurement();
     sensor_readings.temperature = bme280.readTemperature();
     sensor_readings.humidity = bme280.readHumidity();
     sensor_readings.pressure_raw = bme280.readPressure();
   }
-  if (bme680_active) {
+  if (sensors_active.bme680) {
+    bme680.endReading();  // ToDo
     if (bme680.performReading()) {
       sensor_readings.temperature = bme680.temperature;
       sensor_readings.humidity = bme680.humidity;
@@ -174,13 +291,13 @@ void getSensorMeasurements() {
 
   history_pressure.addValue(sensor_readings.pressure);
 
-  if (uv_active) {
+  if (sensors_active.uv) {
     sensor_readings.uvi = uv.readUVI();
     sensor_readings.uva = uv.readUVA();
     sensor_readings.uvb = uv.readUVB();
   }
 
-  if (light_active) {
+  if (sensors_active.light) {
     sensor_readings.lux = lightMeter.readLightLevel();
     // auto-adjust sensitivity
     if (sensor_readings.lux < 0) {
@@ -200,7 +317,7 @@ void getSensorMeasurements() {
     }
   }
 
-  if (sds_active) {
+  if (sensors_active.sds) {
     PmResult pm = sds.readPm();
     if (pm.isOk()) {
       sensor_readings.pm10 = pm.pm10;
@@ -354,7 +471,7 @@ void displayValues() {
     display.printf("%.1f k\xe9", sensor_readings.voc / 1000.0F);
     // PM
     float pm10, pm25;
-    if (sds_active) {
+    if (sensors_active.sds) {
       pm10 = sensor_readings.pm10;
       pm25 = sensor_readings.pm25;
     } else if (!isnan(sensors_a4cf1211c3e4.pm10) || !isnan(sensors_a4cf1211c3e4.pm25)) {
@@ -378,7 +495,7 @@ void displayValues() {
     display.printf("%.1f", pm25);
     // Lux
     float lux;
-    if (light_active) {
+    if (sensors_active.light) {
       lux = sensor_readings.lux;
     } else if (!isnan(sensors_a4cf1211c3e4.lux)) {
       lux = sensors_a4cf1211c3e4.lux;
@@ -395,7 +512,7 @@ void displayValues() {
     display.printf("%.1f lx", lux);
     // UV
     float uvi, uva, uvb;
-    if (uv_active) {
+    if (sensors_active.uv) {
       uvi = sensor_readings.uvi;
       uva = sensor_readings.uva;
       uvb = sensor_readings.uvb;
@@ -449,7 +566,7 @@ void displayValues() {
 
 
 void printValues() {
-  if (bme280_active || bme680_active) {
+  if (sensors_active.bme280 || sensors_active.bme680) {
     #define SEALEVELPRESSURE_HPA (1013.25)
     Serial.print("Temperature = ");
     Serial.print(sensor_readings.temperature);
@@ -468,7 +585,7 @@ void printValues() {
     Serial.println(" %");
   }
 
-  if (bme680_active) {
+  if (sensors_active.bme680) {
     Serial.print("VOC = ");
     Serial.print(sensor_readings.voc / 1000.0F);
     Serial.println(" kOhm");
@@ -476,14 +593,14 @@ void printValues() {
 
   Serial.println();
 
-  if (uv_active) {
+  if (sensors_active.uv) {
     Serial.print("UV Index reading: "); Serial.println(sensor_readings.uvi);
     Serial.print("Raw UVA reading:  "); Serial.println(sensor_readings.uva);
     Serial.print("Raw UVB reading:  "); Serial.println(sensor_readings.uvb);
     Serial.println();
   }
 
-  if (sds_active) {
+  if (sensors_active.sds) {
     Serial.print("PM2.5 = ");
     Serial.print(sensor_readings.pm25);
     Serial.print(", PM10 = ");
@@ -499,63 +616,56 @@ void printValues() {
 
 void sendValues() {
     /* send values MQTT */
-  if (bme280_active || bme680_active) {
+  if (sensors_active.bme280 || sensors_active.bme680) {
     String topic_temperature = String("thomas/sensor/") + ota.getMAC() + String("/temperature");
     String topic_humidity = String("thomas/sensor/") + ota.getMAC() + String("/humidity");
     String topic_pressure = String("thomas/sensor/") + ota.getMAC() + String("/pressure");
-    mqtt.publishf(topic_temperature.c_str(), "%.2f", sensor_readings.temperature);
+    mqtt.publishf2(topic_temperature.c_str(), 1, 1, "%.2f", sensor_readings.temperature);
     delay(10);
-    mqtt.publishf(topic_humidity.c_str(), "%.2f", sensor_readings.humidity);
+    mqtt.publishf2(topic_humidity.c_str(), 1, 1, "%.2f", sensor_readings.humidity);
     delay(10);
-    mqtt.publishf(topic_pressure.c_str(), "%.2f", sensor_readings.pressure);
+    mqtt.publishf2(topic_pressure.c_str(), 1, 1, "%.2f", sensor_readings.pressure);
     delay(10);
   }
-  if (bme680_active) {
+  if (sensors_active.bme680) {
     String topic_voc = String("thomas/sensor/") + ota.getMAC() + String("/voc");
-    mqtt.publishf(topic_voc.c_str(), "%.2f", sensor_readings.voc / 1000.0F);
-    delay(10);
-  }
-  if (!bme280_active && !bme680_active) {
-    String topic_temperature = String("thomas/sensor/") + ota.getMAC() + String("/temperature");
-    float esp32_temperature = (temprature_sens_read() - 32) / 1.8;
-    char temperature[8]; sprintf(temperature, "%.2f", esp32_temperature-29.40);
-    mqtt.publish(topic_temperature.c_str(), temperature, strlen(temperature));
+    mqtt.publishf2(topic_voc.c_str(), 1, 1, "%.2f", sensor_readings.voc / 1000.0F);
     delay(10);
   }
 
-  if (uv_active) {
+  if (sensors_active.uv) {
     String topic_uvi = String("thomas/sensor/") + ota.getMAC() + String("/uvi");
     String topic_uva = String("thomas/sensor/") + ota.getMAC() + String("/uva");
     String topic_uvb = String("thomas/sensor/") + ota.getMAC() + String("/uvb");
-    mqtt.publishf(topic_uvi.c_str(), "%.2f", sensor_readings.uvi);
-    mqtt.publishf(topic_uva.c_str(), "%.2f", sensor_readings.uva);
-    mqtt.publishf(topic_uvb.c_str(), "%.2f", sensor_readings.uvb);
+    mqtt.publishf2(topic_uvi.c_str(), 1, 1, "%.2f", sensor_readings.uvi);
+    mqtt.publishf2(topic_uva.c_str(), 1, 1, "%.2f", sensor_readings.uva);
+    mqtt.publishf2(topic_uvb.c_str(), 1, 1, "%.2f", sensor_readings.uvb);
     delay(10);
   }
 
-  if (light_active) {
+  if (sensors_active.light) {
     String topic_lux = String("thomas/sensor/") + ota.getMAC() + String("/lux");
-    mqtt.publishf(topic_lux.c_str(), "%.2f", sensor_readings.lux);
+    mqtt.publishf2(topic_lux.c_str(), 1, 1, "%.2f", sensor_readings.lux);
     delay(10);
   }
 
-  if (sds_active) {
+  if (sensors_active.sds) {
     String topic_pm10 = String("thomas/sensor/") + ota.getMAC() + String("/pm10");
     String topic_pm25 = String("thomas/sensor/") + ota.getMAC() + String("/pm25");
-    mqtt.publishf(topic_pm10.c_str(), "%.2f", sensor_readings.pm10);
-    mqtt.publishf(topic_pm25.c_str(), "%.2f", sensor_readings.pm25);
+    mqtt.publishf2(topic_pm10.c_str(), 1, 1, "%.2f", sensor_readings.pm10);
+    mqtt.publishf2(topic_pm25.c_str(), 1, 1, "%.2f", sensor_readings.pm25);
     delay(10);
   }
 
   {
     String topic_battery = String("thomas/sensor/") + ota.getMAC() + String("/battery");
-    mqtt.publishf(topic_battery.c_str(), "%.2f", (sensor_readings.battery/4096.0)*2*3.42);
+    mqtt.publishf2(topic_battery.c_str(), 1, 1, "%.2f", (sensor_readings.battery/4096.0)*2*3.42);
     delay(10);
   }
 
   {
     String topic_rssi = String("thomas/sensor/") + ota.getMAC() + String("/rssi");
-    mqtt.publishf(topic_rssi.c_str(), "%d", sensor_readings.rssi);
+    mqtt.publishf2(topic_rssi.c_str(), 1, 1, "%d", sensor_readings.rssi);
     delay(10);
   }
 
@@ -569,7 +679,11 @@ void sendValues() {
 void setup()
 {
   Serial.begin(115200);
-  delay(10);
+
+  esp_sleep_wakeup_cause_t wakeup_reason = esp_sleep_get_wakeup_cause();
+  ++bootCount;
+  Serial.println("Boot number: " + String(bootCount));
+  Serial.println("millis(): " + String(millis()));
 
   ESP_LOGD(TAG, "setup hardware and sensors");
 
@@ -583,20 +697,21 @@ void setup()
   adcAttachPin(_VBAT);
   adcStart(_VBAT);
 
-  // initialize e-paper display
-  SPI.begin(18, 19, 23, TFT_CS); // MISO is not connected to TFT_MISO!
-  display.init();
+  Serial.println("millis(): " + String(millis()));
 
   #define BME_SDA 21
   #define BME_SCL 22
   Wire.begin(BME_SDA, BME_SCL);
   if (bme280.begin()) {
-    bme280_active = true;
+    sensors_active.bme280 = true;
   } else {
     ESP_LOGE(TAG, "Could not find a valid BME280 sensor, check wiring!");
   }
+
+  Serial.println("millis(): " + String(millis()));
+
   if (bme680.begin()) {
-    bme680_active = true;
+    sensors_active.bme680 = true;
 
     // Set up oversampling and filter initialization
     bme680.setTemperatureOversampling(BME680_OS_8X);
@@ -604,12 +719,15 @@ void setup()
     bme680.setPressureOversampling(BME680_OS_4X);
     bme680.setIIRFilterSize(BME680_FILTER_SIZE_3);
     bme680.setGasHeater(320, 150); // 320*C for 150 ms
+    bme680.beginReading();
   } else {
     ESP_LOGE(TAG, "Could not find a valid BME680 sensor, check wiring!");
   }
 
+  Serial.println("millis(): " + String(millis()));
+
   if (uv.begin()) {
-    uv_active = true;
+    sensors_active.uv = true;
 
     uv.setIntegrationTime(VEML6075_100MS);  // Set the integration constant
     uv.setHighDynamic(true);  // Set the high dynamic mode
@@ -622,55 +740,66 @@ void setup()
     Serial.println("Failed to communicate with VEML6075 sensor, check wiring?");
   }
 
+  Serial.println("millis(): " + String(millis()));
+
   if (lightMeter.begin()) {
-    light_active = true;
+    sensors_active.light = true;
   } else {
     Serial.println("Failed to communicate with BH1750 sensor, check wiring?");
   }
 
+  Serial.println("millis(): " + String(millis()));
+
   sds.begin();
 
-  FirmwareVersionResult sds_fw = sds.queryFirmwareVersion();
-  if (sds_fw.isOk()) {
-    sds_active = true;
+  Serial.println("millis(): " + String(millis()));
 
-    sds.setActiveReportingMode();  // ensures sensor is in 'active' reporting mode
-    sds.setCustomWorkingPeriod(5); // sensor sends data every 3 minutes
-  } else {
-    Serial.println("Failed to communicate with SDS011 sensor, check wiring?");
+  if (wakeup_reason == ESP_SLEEP_WAKEUP_UNDEFINED || bootCount == 1) {
+    FirmwareVersionResult sds_fw = sds.queryFirmwareVersion();
+    if (sds_fw.isOk()) {
+      sensors_active.sds = true;
+
+      sds.setActiveReportingMode();  // ensures sensor is in 'active' reporting mode
+      sds.setCustomWorkingPeriod(5); // sensor sends data every 3 minutes
+    } else {
+      Serial.println("Failed to communicate with SDS011 sensor, check wiring?");
+    }
   }
 
-  //display.clearScreen();
-  //display.refresh();
+  Serial.println("millis(): " + String(millis()));
 
-  ESP_LOGD(TAG, "displaying welcome screen");
-  helloWorld();
-  display.powerOff();
+  // initialize e-paper display
+  SPI.begin(18, 19, 23, TFT_CS); // MISO is not connected to TFT_MISO!
+  display.init(0, false, false);
+  display.setRotation(1);
 
-  ESP_LOGD(TAG, "connecting to WiFi");
+  Serial.println("millis(): " + String(millis()));
 
-  WiFi.setHostname("esp32-weatherstation");
+  if (wakeup_reason == ESP_SLEEP_WAKEUP_UNDEFINED || bootCount == 1) {
+    // wakeup not caused by deep sleep
+    display.clearScreen();
+    display.refresh();
+    helloWorld();
+    display.powerOff();
+  } else {
+    // wakeup by deep sleep
+//    displayValues();
+  }
 
-  wifiMulti.addAP(WIFI_SSID, WIFI_PASSWD);
-  wifiMulti.addAP(WIFI_SSID2, WIFI_PASSWD2);
-  wifiMulti.addAP(WIFI_SSID3, WIFI_PASSWD3);
+  ESP_LOGD(TAG, "connecting to WiFi");
+  Serial.println("millis(): " + String(millis()));
 
-  for (int tries=0; wifiMulti.run() != WL_CONNECTED && tries < 10; tries++) {
-    Serial.print(".");
-    delay(500);
-  }
+  wifiConnect();
 
-  if(wifiMulti.run() == WL_CONNECTED) {
-    Serial.println("");
-    Serial.println("WiFi connected");
-    Serial.println("IP address: ");
-    Serial.println(WiFi.localIP());
-    displayIcoPartial(ico_wifi16, display.width()-20, y_offset+0, ico_wifi16_width, ico_wifi16_height);
-  }
+  WiFi.waitForConnectResult();
+  //displayIcoPartial(ico_wifi16, display.width()-20, y_offset+0, ico_wifi16_width, ico_wifi16_height);
 
-  ESP_LOGD(TAG, "trying to fetch over-the-air update");
-  if (WiFi.status() == WL_CONNECTED) {
-    ota.update();
+  if (wakeup_reason == ESP_SLEEP_WAKEUP_UNDEFINED || bootCount == 1) {
+    // wakeup not caused by deep sleep
+    ESP_LOGD(TAG, "trying to fetch over-the-air update");
+    if (WiFi.status() == WL_CONNECTED) {
+      ota.update();
+    }
   }
 
   WiFi.setSleep(true);
@@ -684,7 +813,6 @@ void setup()
   if (!ota.getMAC().equals("246f28d1eff4")) mqtt.subscribe("thomas/sensor/246f28d1eff4/#", receiveMqtt);
 
   /* temp: publish version */
-  delay(5000);
   String topic_version = String("thomas/sensor/") + ota.getMAC() + String("/version");
   const char* fw_version_str = String(FW_VERSION).c_str();
   mqtt.publish(topic_version.c_str(), fw_version_str, strlen(fw_version_str));
@@ -705,27 +833,27 @@ void setup()
  */
 void loop()
 {
-  /* Do an e-paper display refresh every 1 minutes */
-  if (millis() - lastDisplayUpdate >= 1*60*1000) {
-    lastDisplayUpdate = millis();
+/*  if(wifiMulti.run() != WL_CONNECTED) {
+    Serial.println("WiFi not connected!");
+    delay(1000);
+  }*/
 
     /* Do a full refresh every hour */
-    if (millis() - lastDisplayRefresh >= 60*60*1000) {
-      lastDisplayRefresh = millis();
-      display.clearScreen();
-      display.refresh();
-    }
-
-    getSensorMeasurements();
-    displayValues();
-    printValues();
-    sendValues();
+  if (getTimestamp() - lastDisplayRefresh >= 60*60) {
+    Serial.printf("last display refresh :%ds ago", getTimestamp() - lastDisplayRefresh);
+    lastDisplayRefresh = getTimestamp();
+    display.clearScreen();
+    display.refresh();
   }
 
-  if(wifiMulti.run() != WL_CONNECTED) {
-    Serial.println("WiFi not connected!");
-    delay(1000);
-  }
+  getSensorMeasurements();
+  displayValues();
+  printValues();
+  sendValues();
+
+  int runtime = millis()/1000;
+  if (runtime < 0 || runtime >= TIME_TO_SLEEP) runtime = 0;
 
+  gotoSleep(TIME_TO_SLEEP - runtime);
   delay(2000);
 }